Orthopox Virus Infections in Eurasian Wild Rodents Paula M. Kinnunen, 1,7, * Heikki Henttonen, 2 Bernd Hoffmann, 3 Eva R. Kallio, 2,4,{ Christian Korthase, 3 Juha Laakkonen, 2,{ Jukka Niemimaa, 2 Airi Palva, 1 Mathias Schlegel, 5 Hanan Sheikh Ali, 5,6 Paula Suominen, 1,§ Rainer G. Ulrich, 5 Antti Vaheri, 7,8 and Olli Vapalahti 1,7,8 Abstract The genus Orthopoxvirus includes variola (smallpox) virus and zoonotic cowpox virus (CPXV). All ortho- poxviruses (OPV) are serologically cross-reactive and cross-protective, and after the cessation of smallpox vaccination, CPXV and other OPV infections represent an emerging threat to human health. In this respect CPXV, with its reservoir in asymptomatically infected wild rodents, is of special importance. In Europe, clinical cowpox has been diagnosed in both humans and animals. The main objective of this study was to elucidate the prevalence of OPV infections in wild rodents in different parts of Eurasia and to compare the performance of three real-time polymerase chain reaction (PCR) methods in detecting OPV DNA in wildlife samples. We investigated 962 wild rodents from Northern Europe (Finland), Central Europe (Germany), and Northern Asia (Siberia, Russia) for the presence of OPV antibodies. According to a CPXV antigen-based immunofluorescence assay, animals from 13 of the 17 locations (76%) showed antibodies. Mean seroprevalence was 33% in Finland (variation between locations 0%–69%), 32% in Germany (0%–43%), and 3.2% (0%–15%) in Siberia. We further screened tissue samples from 513 of the rodents for OPV DNA using up to three real-time PCRs. Three rodents from two German and one Finnish location were OPV DNA positive. The amplicons were 96% to 100% identical to available CPXV sequences. Further, we demonstrated OPV infections as far east as the Baikal region and occurring in hamster and two other rodent species, ones previously unnoticed as possible reservoir hosts. Based on serological and PCR findings, Eurasian wild rodents are frequently but nonpersistently infected with OPVs. Results from three real-time PCR methods were highly concordant. This study extends the geographic range and wildlife species diversity in which OPV (or CPXV) viruses are naturally circulating. Key Words: Antibodies—Cowpox virus—Distribution—PCR—Rodent. Introduction T he genus Orthopoxvirus within the family Poxviridae contains several serologically cross-reactive and cross- protective virus species (Damon 2007). The best-known ex- ample, variola (smallpox) virus, was eradicated in 1978 by vaccination with another orthopoxvirus (OPV) species, vac- cinia virus (VACV). Consequently, vaccinations were discontinued, resulting in waning antibody prevalence (Pelkonen et al. 2003). This predisposes mankind to other OPVs, for instance, monkeypox virus (MPXV) and cowpox virus (CPXV), the latter being Europe’s most common OPV infection (Essbauer et al. 2010). Increasing cowpox inci- dence in humans is already evident in those young and unvaccinated (Nitsche and Pauli 2007). Cowpox typically manifests with painful skin lesions and constitutional symp- 1 Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland. 2 METLA, Finnish Forest Research Institute, Vantaa Research Centre, Vantaa, Finland. 3 Friedrich-Loeffler-Institut, Institute for Diagnostic Virology, Greifswald-Insel Riems, Germany. 4 Department of Biological and Environmental Science, University of Jyva ¨ skyla ¨, Jyva ¨ skyla ¨ , Finland. 5 Friedrich-Loeffler-Institut, Institute for Novel and Emerging Infectious Diseases, Greifswald-Insel Riems, Germany. 6 College of Veterinary Medicine, Sudan University of Science and Technology, Khartoum, Sudan. 7 Haartman Institute, University of Helsinki, Helsinki, Finland. 8 HUSLAB, Helsinki University Central Hospital, Helsinki, Finland. *Present address: Centre for Military Medicine, Research and Development Department, Helsinki, Finland. { Present address: Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom. { Present address: Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland. § Present address: Veterinary Practice, City of Kuusamo, Kuusamo, Finland. VECTOR-BORNE AND ZOONOTIC DISEASES Volume 11, Number 8, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089/vbz.2010.0170 1133